Prevent window from closing while uploading data

lib/utils/data_sync.dart

@@ -1,4 +1,6 @@
 import 'package:flutter/foundation.dart';
+import 'package:venera/components/components.dart';
+import 'package:venera/components/window_frame.dart';
 import 'package:venera/foundation/app.dart';
 import 'package:venera/foundation/appdata.dart';
 import 'package:venera/foundation/comic_source/comic_source.dart';
@@ -10,6 +12,7 @@ import 'package:venera/utils/data.dart';
 import 'package:venera/utils/ext.dart';
 import 'package:webdav_client/webdav_client.dart' hide File;
 import 'package:rhttp/rhttp.dart' as rhttp;
+import 'package:venera/utils/translations.dart';
 
 import 'io.dart';
 
@@ -20,6 +23,10 @@ class DataSync with ChangeNotifier {
     }
     LocalFavoritesManager().addListener(onDataChanged);
     ComicSourceManager().addListener(onDataChanged);
+    Future.delayed(const Duration(seconds: 1), () {
+      var controller = WindowFrame.of(App.rootContext);
+      controller.addCloseListener(_handleWindowClose);
+    });
   }
 
   void onDataChanged() {
@@ -28,6 +35,28 @@ class DataSync with ChangeNotifier {
     }
   }
 
+  bool _handleWindowClose() {
+    if (_isUploading) {
+      _showWindowCloseDialog();
+      return false;
+    }
+    return true;
+  }
+
+  void _showWindowCloseDialog() async {
+    showLoadingDialog(
+      App.rootContext,
+      cancelButtonText: "Shut Down".tl,
+      onCancel: () => exit(0),
+      barrierDismissible: false,
+      message: "Uploading data...".tl,
+    );
+    while (_isUploading) {
+      await Future.delayed(const Duration(milliseconds: 50));
+    }
+    exit(0);
+  }
+
   static DataSync? instance;
 
   factory DataSync() => instance ?? (instance = DataSync._());